Scapulothoracic arthrodesis (STA) is a well-established surgical technique to provide scapular stabilization in patients with facioscapulohumeral dystrophy (FSHD). There is no staging or scoring systems available to guide surgical decision. The aim of this study was to develop a staging system to evaluate the shoulder disability in patients with FSHD to guide surgical decision making and assess its reliability among surgeons.

Fifty-seven shoulders of 29 patients (15 male, 14 female) with an average age of 34.5 years (13–73) were included. Six stages of the disease were defined to create a system consisting of shoulder elevation, deltoid function and scapular winging. Patients were assessed by two independent orthopaedic surgeons who were blind to each other. Statistical analyses included mean and standard deviation for descriptive variables, Pearson's correlation and Cohen's Kappa for inter and intra observer agreement.

Measurement of elevation showed excellent correlation in both inter- and intraobserver assessment. There was substantial agreement on deltoid function and moderate agreement on scapular winging. Decision on stage showed excellent agreement on inter observer and substantial agreement on intra observer assessment. Surgical decision using the stage showed excellent agreement on both inter and intra observer assessment.

This novel staging system has an excellent inter observer agreement on FSHD patients’ shoulder disability. This would provide surgeons a beneficial tool to define patient groups that would have negatively or positively affected from STA.